Fw: FAT-FS HD write speed

[Leon Pollak]

On Saturday 11 January 2003 09:17, Thomas Doerfler wrote:
Hello,
	Our product is heavily based on ATA Flash cassettes writing and we also 
invested a lot of efforts to measure and speed up writing process.
> today I have run the write data rate test. My system is a
> MC68040 with a Sandisk PCMCIA Flash Disk attached.
Our case seems similar - MPC860 running at 25MHz.

> for the flash disk I got data rates of 78KByte/sec, for the
> ramdisk I reached 380KByte/sec.
As you probably remember I have my own FAT16 implementation. Recently I 
totally rewrote my cassettes HW driver and run performance tests. My result 
for the new, very improved for speed driver on my 25MHz system with SanDisk 
80MB cassettes is 156KB/s. I underline here that the result is concerning 
PURE driver - one sector by sector writing.
You can significantly improve the write speed by means of multisector writing, 
but this is totally different story, which we have implemented totally 
different.

> - The Fats get written too often: It might be sufficent to
> update them, whenever a file is closed, I think this happens
> now whenever a new block is allocated, or so.
I do not know your FAT implementation. Our is kept in RAM (with some tricks 
for unexpected power-down recovery) and still, our results with the old 
driver (which WAS NOT SO BAD WRITTEN!) were very similar - 87KB/s.


> - The write function of our driver migt be somewhat slow. It
> has been written for "robust" functionality, not speed.
See above.

My personal estimation is that using our new driver (with different cassette 
wait ready manner), DMA and zero-copy FAT code we shall be able to reach not 
more then 160-170KB/s - this seems to be the natural limitation of flash 
disks.

> I hope this information helps you on...
Me too...:-)))

-- 
Dr.Leon M.Pollak
Director
PLR Information Systems Ltd.
leonp at plris dot com